If you don't know which framework to use..

... look here

Mac OS X newbies

Perhaps this thread should be read by all Win to OS-X convertees. Although it's a little long it's worth scanning through it.

OS-X Simple Graphic Tools

One thing - apart from the cd-copy stuff - that really bugs me in OS-X is the absence of anything even remotely resembling MS-Paint. I suppose most Mac users own some Version of Photoshop or the like but I'm a consultant and developer not an artist that's why I'd like to have something lightweight, easy and free.
After some googling I found
Seashore (probably a little heavy)
Seashore
Seashore
and
Posterpaint

let's have a look at them... more to come
-mm

P.S.: Drawing could be done with
Inkscape or
ArtRage 2.1